When a vertical-type semiconductor device is formed on a semiconductor substrate (hereinafter, referred to as wafer), a thickness of the wafer is reduced by grinding and polishing, for example, a back surface of the wafer. After that, the back surface of the wafer having a reduced thickness is subjected to various types of processing such as formation of electrodes on the back surface.
In the process of reducing the thickness of the wafer, a surface protection tape (hereinafter, referred to as back side grinding (BSG) tape) is bonded on a side of a main surface of the wafer before the thickness of the wafer is reduced by grinding and polishing, for example, the back surface of the wafer. The BSG tape needs to be peeled off after the thickness of the wafer is reduced.
Conventionally, the peeling of the BSG tape is performed in the following manner. A wafer is placed on an absorption stage such that a back surface of the wafer is oriented downwards. A peeling tape is pressure-bonded to a BSG tape bonded to a main surface of the wafer. The BSG tape and the peeling tape are removed together from the main surface of the wafer. Thus, the BSG tape is peeled off.
However, in the conventional peeling method, the wafer is placed on the absorption stage such that the back surface of the wafer is oriented downwards, and hence there may be that particles (dust) or contaminants (e.g., organic matters and metals) adhere to the back surface of the wafer, the wafer is damaged due to mechanical contact, and so on.
When particles adhere to the back surface of the wafer, there may be that electrodes on the back surface formed by sputtering are detached or defects occur during resist coating or light exposure in a photolithography process. Moreover, upon implantation of impurity ions in an ion implantation process, there may be that impurity ions are not implanted in some areas because such particles may function as an ion-shielding material (block material).
Further, when contaminants adhere to the wafer, there is a fear that a conductive type of a channel of a semiconductor device is reversed during a diffusion process (e.g., thermal diffusion and laser annealing) or the lifetime of carrier is below a standard value. Moreover, if the wafer is damaged due to mechanical contact, there is a fear that a break or crack occurs in the wafer and the back surface of the wafer cannot be subjected to processing.